Charger for dry galvanic cells using asymmetrical current

ABSTRACT

An improved charging circuit apparatus for charging both &#34;rechargeable&#34; and &#34;non-rechargeable&#34; batteries from an AC power source utilizing capacitors and two diodes. The anode of the first diode is connected to a first output terminal and a first input terminal; the first diode&#39;s cathode being connected to the anode of the second diode, the cathode of the second diode being connected to a second output terminal. The capacitors are connected to the second input terminal. One capacitor is further connected to the cathode of the first diode and therefore anode of the second. A second capacitor is further connected to the second output terminal. A current limiting circuit is also provided which is connected to the charging circuit to provide protection against overcharging of the batteries.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of our application Ser. No. 08/016,833 filed Feb. 12, 1993 now abandoned.

FIELD OF THE INVENTION

The present invention relates to an apparatus for the desulphation, charging, and the prevention of sulphation of batteries, and more particularly to a battery charger apparatus capable of repeatedly charging dry cells, including galvanic, alkaline, lithium, mercury oxide, silver oxide, zinc-carbon, zinc chloride, and nickel-cadmium batteries, both rechargeable and non-rechargeable, as well as wet cells, including leads-acid batteries, by asymmetrical current from an alternating current source.

BACKGROUND OF THE INVENTION

A battery charger normally employs a large, expensive, and heavy transformer for stepping down the AC line voltage to a value compatible with the battery voltage. This known charger can only recharge so called "rechargeable batteries, such as lead-acid batteries. So called transformer-less battery chargers are also well known in the art. These generally use a diode bridge circuit requiring at least four diodes and are also limited to charging (or recharging) of rechargeable batteries.

Throughout this specification, the "term desulphation" means the cleaning of the battery terminals.

The present invention includes a circuit capable of charging both rechargeable and non-rechargeable dry galvanic cells using a transformer-less circuit having a minimum number of components, thereby minimizing the cost and size of the apparatus. Further, the charging current is not influenced by the number of batteries being charged, but rather is determined by the accumulating capacity of the circuit.

DESCRIPTION OF RELATED ART

Applicants are aware of the following U.S. Patents concerning transformer-less battery chargers.

    ______________________________________                                         U.S. Pat. No.                                                                           Issue Date                                                                               Inventor  Title                                             ______________________________________                                         3,013,198                                                                               12-12-1961                                                                               Witte     CELL UNIT FOR                                                                  INSERTION INTO A                                                               FLASHLIGHT                                        3,176,212                                                                               03-30-1965                                                                               De Puy    DIRECT CURRENT                                                                 POSER SUPPLIES                                    3,382,425                                                                               05-07-1968                                                                               Legatti   BATTERY CHARGER                                   3,708,738                                                                               01-02-1973                                                                               Crawford  BATTERY CHARG-                                                                 ING AND DIS-                                                                   CHARGE APPARAT-                                                                US                                                3,867,682                                                                               02-18-1975                                                                               Yamauchi  BATTERY CHARGER                                                                WITH MEANS FOR                                                                 PREVENTING                                                                     OVERCHARGING OF                                                                THE BATTERY                                       3,876,921                                                                               04-08-1975                                                                               Bigbee    INTEGRATED                                                                     REJUVENABLE                                                                    ENERGY SYSTEM                                                                  AND METHOD                                        3,970,912                                                                               07-20-1976                                                                               Hoffman   BATTERY CHARG-                                                                 ING CIRCUIT                                       3,987,354                                                                               10-19-1976                                                                               Mason     REGULATING                                                                     CIRCUIT                                           4,146,825                                                                               03-27-1979                                                                               Harhay    ELECTRIC                                                                       BATTERY POWER-                                                                 ED VEHICLE                                        4,321,523                                                                               02-23-1982                                                                               Hammel    BATTERY CHARGER                                                                AND POWER                                                                      SUPPLY CIRCUITRY                                  4,389,608                                                                               06-21-1983                                                                               Dahl      TRANSFORMERLESS                                                                BATTERY CON-                                                                   TROLLED BATTERY                                                                CHARGER                                           4,472,672                                                                               09-18-1984                                                                               Pacholok  HIGH POWER                                                                     FACTOR SWITCH-                                                                 ING-TYPE BATTERY                                                               CHARGER                                           4,621,225                                                                               11-04-1986                                                                               Birk      PASSIVE TRANS-                                                                 FORMERLESS                                                                     BATTERY CHARG-                                                                 ING UNIT                                          ______________________________________                                    

While some of the above mentioned patents have features of the present invention, all are lacking in some respect. Most of the above patents require extensive circuitry and have operational limitations, and none are designed to operate on non-rechargeable batteries. Of those listed above, Witte, Birk and Mason are the most relevant.

Witte shows a rechargeable cell unit wherein the line voltage is applied to a voltage divider across a discharge resistor. By using the dry rectifier to provide resistance, the charging rectifier is protected against high voltage peaks occurring in the changing voltage.

Birk also shows a flashlight battery charging circuit. However in Birk, the line voltage is supplied through a coupling capacitor and then is full-wave rectified. The storage capacitor is charged during alternate half cycles of the AC supply voltage to a relatively high voltage. On the remaining half cycle the storage capacitor discharges through an LED and a resistor to supply the battery a limited current at a relatively high voltage.

Mason shows a regulating circuit that can be used for charging where the current is regulated to be independent of the load.

SUMMARY OF THE INVENTION

The present invention relates to an improved battery charging circuit which avoids the disadvantages of prior charging circuits while affording additional structural and operating advantages.

A charging circuit for charging both rechargeable and non-rechargeable batteries from an AC power source utilizing capacitors and two diodes. The anode of the first diode is connected to a first output terminal and a first input terminal; the first diode's cathode is connected to the anode of the second diode whose cathode is connected to a second output terminal. The capacitors are connected to the second input terminal. One capacitor is further connected to the cathode of the first diode and therefore anode of the second. A second capacitor is further connected to the second output terminal.

OBJECTS OF THE INVENTION

The principal object of the invention is to provide an improved apparatus for desulphation, charging and preventing the sulphation of batteries.

Another object of this invention is to provide apparatus for charging dry galvanic cells by asymmetrical current from alternating current.

Another object of the invention is to provide apparatus for charging a number of cells wherein the accumulating capacity of the device and not the charge time influences the value of charging current.

Another object of the invention is to provide apparatus for controlling the current to the cells to be charged when cells are sufficiently recharged so as to prevent overcharging.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects will become more readily apparent by referring to the following detailed description and the appended drawings in which:

FIG. 1 is a schematic circuit diagram of a battery charging circuit constructed in accordance with and embodying the features of the present invention.

FIG. 2 is a schematic circuit diagram of the battery charging circuit with additional circuitry provided to prevent overcharging of the batteries.

DETAILED DESCRIPTION

Referring now to FIG. 1, the invented circuit includes input terminals 1 and 2, adapted to be connected to a source of alternating current (120 v, 60 Hz, or 220 v, 50 Hz) and output terminals 10 and 11 being adapted for connection with terminals 12 through 24 which are adapted to be connected to the cells to be recharged. Input terminal 1 is connected respectively to the anode of diode 6 and to negative output terminal 10. The cathode of diode 6 is connected respectively to the anode of diode 7 and capacitor 3 whose other terminal is connected to input terminal 2. Input terminal 2 is also connected to capacitor 5. The other terminal of capacitor 5 in turn being connected to output terminal 11 and to the cathode of light emitting diode 8. The anode of light emitting diode 8 is connected to the cathode of diode 7. Light emitting diode 8 is connected in parallel to resistor 9 and capacitor 4. It is to be understood that the purpose of capacitor 4 and resistor 9 is to limit the current through light emitting diode 8 and, if an incandescent bulb is used as an indicator, they are not installed.

In operation, alternating line voltage is brought up to terminals 1 and 2. In the phase when plus is applied to the anode of diode 6 and minus to capacitor 3, capacitor 3 commences charging. This continues until capacitor 3 reaches the amplitudinal value of the source line voltage after which diode 6 is blocked. The voltage of one side of capacitor 3 is positive when compared to the other side and "zero" when compared to the circuit of line source and capacitor 3. During this semi-period, the line current is flowing in the circuit comprised of input terminal 1, output terminal 10, terminals 12 through 24, batteries, output terminal 11, capacitor 5, and finally input terminal 2.

From the start of the second half of this semi-period the voltage in the circuit of line source and capacitor 3 is gradually increasing to the battery's voltage. When the voltage of this circuit equals that of the battery, diode 7 opens and capacitor 3 starts to discharge to the battery via the circuit diode 7, resistor 9, battery, and line source.

When the polarity of the line voltage changes, the charging current continues to run until the voltage of the line source and capacitor 3 is equal to that of the batteries, whereupon capacitor 3 is charged with opposite polarity. When diode 7 is open the potentials of capacitors 3 and 5 are equalized by current running in the circuit capacitor 3, diode 7, resistor 9, and capacitor 5. Once the charging current is completed the device structure changes again. Capacitor 3 is again charged to the amplitudinal value of the line voltage, whereupon the described process repeats cyclically with the line voltage frequency.

If the voltage of the battery is higher than the amplitudinal value of the source voltage the process repeats but without capacitor 3 recharging. Instead, capacitor 3 is extra charged by the source and discharged to the battery. The capacitive resistance of capacitor 3 thus limits the battery charging current. During charging, capacitor 3 is connected with the line source consecutively-correspondingly, and, therefore is an extra voltage source. The battery is charged up to double the value of the amplitude of the line source voltage.

The actual amount the batteries will be charged is dependant on the quality of the battery, and more specifically the hermetic seal of the cell. In general, dry galvanic cells can be restored to greater than 80% of their electrical capacity through the use of the disclosed circuit.

The preferred embodiment of the inventive charger is shown in FIG. 2. The circuit shown is identical to that shown in FIG. 1 with several additions. The identical identification numbers used in both figures signify identical parts. Capacitor 26 and resistor 27 are connected in parallel to capacitor 3. Resistor 36 is connected in series with the LED 8 to limit the current through the LED 8. A control circuit 37 is connected to the charging circuit to prevent overcharging of the cells that are connected between output terminals 10 and 11.

The control circuit 37 comprises a diode 28 the anode of which is connected to the cathode of diode 6 and the anode of diode 7. The cathode of diode 28 is connected in series to resistor 29 which is connected to the anode of silicon controlled rectifier 30. The gate of SCR 30 is connected to the anode of zener diode 32 and to one terminal of resistor 31. The other terminal of resistor 31 is connected to the cathode of SCR 30. The cathode of SCR 30 is connected to output terminal 10. The cathode of zener diode 32 is connected to the wiper of potentiometer 33. One terminal of potentiometer 33 is connected in series to resistor 35 and the other terminal is connected to resistor 34. The other terminal of resistor 34 is connected to output terminal 11, while the second terminal of resistor 35 is connected to output terminal 10.

In operation, the potentiometer is adjusted by the user of the charger and is set to a level corresponding to the number and type of battery cell that is to be placed in the charger between output terminals 10 and 11. When the cells are sufficiently recharged by the operation of the circuit as described above and when terminal 2 is positive with respect to terminal 1, diode 7 and diode 28 are on and diode 6 is off. The increased voltage between terminals 10 and 11 due to sufficient recharging of the batteries creates a breakdown voltage in the zener diode 32. Due to the high resistance of the recharged cells between terminals 10 and 11, current is diverted from the cells and flows through resistor 34. Reverse current then flows through the zener diode 32 and into the gate of SCR 30. SCR 30 is thus activated so that current flows from the anode to the cathode of the SCR. This draws current from the charging circuit, thus bypassing the recharged cells and avoiding overcharging.

When terminal 1 is positive with respect to terminal 2, diode 28 and diode 7 are both off and diode 6 is on. Current flows through the circuit of diode 6, capacitor 5, and series resistors 34, 33, and 35.

ALTERNATIVE EMBODIMENTS

The circuit described above can be modified to handle a variety of batteries of varying capacity, including galvanic, alkaline, lithium, mercury oxide, silver oxide, zinc-carbon, zinc chloride, and nickel-cadmium batteries, both rechargeable and non-rechargeable, as well as wet cells, including lead-acid batteries. Since the charging current does not depend on the load value, i.e., on the number and types of simultaneous charged cells, but depends on the accumulating capacity of capacitor 3, a simple light indicator could replace the light diode. Further enhancements can be made to the circuit to increase the functionality or safety of the device. For example, a switch can be added that disconnects the line voltage when the user is loading the device with batteries. The unit can be constructed in the same case as the battery, thereby eliminating the charging stand. Further, due to the limited circuitry involved, the charging device and the battery can be constructed directly into the appliance in which it is being used.

SUMMARY OF THE ACHIEVEMENT OF THE OBJECTS OF THE INVENTION

From the foregoing, it is readily apparent that we have invented an improved method and apparatus for the desulphation and charging of dry cell and wet cell batteries, both of the rechargeable and non-rechargeable type, more economically than heretofore has been possible.

It is to be understood that the foregoing description and specific embodiments are merely illustrative of the best mode of the invention and the principles thereof, and that various modifications and additions may be made to the apparatus by those skilled in the art, without departing from the spirit and scope of this invention, which is therefore understood to be limited only by the scope of the appended claims. 

What is claimed is:
 1. A circuit for charging batteries with asymmetrical current from an AC supply voltage, said circuit comprising:a first input terminal and a second input terminal, said input terminals having connector means for connection to said AC supply voltage; a first output terminal and a second output terminal, said output terminals having connector means for connection to said batteries; a first diode having an anode and a cathode, the anode of said first diode being connected to said first output terminal and to said first input terminal; a second diode having an anode and a cathode, the cathode of said second diode being connected to said second output terminal; a first capacitor having two terminals, one of said capacitor terminals being connected to said second input terminal, the other of said capacitor terminals being connected to the cathode of said first diode and the anode of said second diode; a second capacitor having two terminals, one of said terminals being connected to said second input terminal, the other of said terminals being connected to said second output terminal; and means for limiting current flow through said batteries connected to said output terminals after said batteries have been charged to a predetermined level, said current limiting means comprising:a third diode having an anode and a cathode; a first resistor having two terminals; a silicon controlled rectifier having an anode, a cathode, and a gate; a second resistor having two terminals; a zener diode having an anode and a cathode; a third resistor having two terminals; a fourth resistor having two terminals; a potentiometer having three terminals, one of which is adjustable to vary the resistance of said potentiometer; said anode of said third diode being connected to said cathode of said first diode; one of said first resistor terminals being connected to said cathode of said third diode and the other of said terminals of said first resistor being connected to said anode of said silicon controlled rectifier; said gate of said silicon controlled rectifier being connected to said anode of said zener diode and to one terminal of said second resistor; the cathode of said silicon controlled rectifier being connected to a second terminal of said second resistor and to said first output terminal; the cathode of said zener diode being connected to said adjustable terminal of said potentiometer; one of said terminals of said third resistor being connected to said second output terminal, the other of said terminals of said third resistor being connected to one of said terminals of said potentiometer; one of said terminals of said fourth resistor being connected to a second of the terminals of said potentiometer, the other of said other terminals of said fourth resistor being connected to said first output terminal.
 2. The circuit according to claim 1 further comprising indicating means responsive to the charging current for indicating that the circuit is operative.
 3. The circuit according to claim 1 further comprising switching means for disconnecting the AC supply voltage in the absence of the batteries to be charged.
 4. The circuit according to claim 1 wherein the batteries to be charged are dry cell batteries.
 5. The circuit according to claim 4 wherein the batteries to be charged are selected from the group consisting of galvanic, alkaline, lithium, mercury oxide, silver oxide, zinc-carbon, zinc chloride, and nickel-cadmium batteries, both rechargeable and non-rechargeable.
 6. The circuit according to claim 1 wherein the batteries to be charged are wet cell batteries.
 7. The circuit according to claim 1 further comprising a fifth resistor and a third capacitor, said fifth resistor and said third capacitor being shunted across said first capacitor.
 8. The circuit according to claim 2 wherein said indicating means comprises a light emitting diode having an anode and a cathode, the cathode being connected to said second output terminal and the anode being connected to the cathode of said second diode.
 9. The circuit according to claim 8 further comprising a sixth resistor connected between said cathode of said second diode and said anode of said light emitting diode.
 10. The circuit according to claim 9 further comprising a seventh resistor and a fourth capacitor each having first and second terminals, each first terminal being connected to the cathode of said first diode and each second terminal being connected to said second output terminal. 